1+ import java .util .*;
2+
3+ public class MyLinkedList implements List {
4+
5+ private Node first ;
6+ private Node last ;
7+ private int size = 0 ;
8+ public void Myadd (Object o ){
9+ final Node l = last ;
10+ final Node newNode = new Node (l ,o ,null );
11+ last = newNode ;
12+ if (l == null )
13+ first = newNode ;
14+ else
15+ l .next = newNode ;
16+ size ++;
17+ }
18+ public void Myadd (int index , Object o ){
19+ checkPosition (index );
20+ if (index == size ){
21+ Myadd (o );
22+ }
23+ else {
24+ final Node PreNode =GetNodeByIndex (index ).prev ;
25+ final Node newNode = new Node (PreNode ,o ,GetNodeByIndex (index ));
26+ PreNode .next =newNode ;
27+ if (PreNode == null )
28+ first = newNode ; //ΪʲôҪ¸¶¸øÊ×Ö¸Õ룿
29+ else
30+ PreNode .next = newNode ;
31+ size ++;
32+ }
33+ }
34+ public Object get (int index ){
35+ checkPosition (index );
36+ return GetNodeByIndex (index );
37+ }
38+ public void remove (int index ){
39+ Node node = GetNodeByIndex (index );
40+ node .prev .next = node .next ;
41+ node .next .prev = node .prev ;
42+ node = null ;
43+ size --;
44+ }
45+
46+ public int size (){
47+ return size ;
48+ }
49+
50+ public void addFirst (Object o ){
51+ final Node FirstNode = first ;
52+ final Node newNode = new Node (null ,o ,first );
53+ first = newNode ;
54+ if (FirstNode == null )
55+ last = newNode ;
56+ else
57+ first .prev = newNode ;
58+ size ++;
59+
60+ }
61+ public void addLast (Object o ){
62+ final Node LastNode = last ;
63+ final Node newNode = new Node (last ,o ,null );
64+ last = newNode ;
65+ if (last == null )
66+ first = newNode ;
67+ else
68+ last .next = newNode ;
69+ size ++;
70+ }
71+ public void removeFirst (){
72+ final Node f = first ;
73+ if (f == null )
74+ throw new NoSuchElementException ();
75+ first = f .next ;
76+ first = null ;
77+ size --;
78+ }
79+ public void removeLast (){
80+ final Node f = last ;
81+ if (f == null )
82+ throw new NoSuchElementException ();
83+ last = last .prev ;
84+ last = null ;
85+ size --;
86+ }
87+ public Iterator iterator (){
88+ return null ;
89+ }
90+
91+
92+ private static class Node {
93+ Object item ;
94+ Node next ;
95+ Node prev ;
96+ Node (Node prev ,Object element ,Node next ){
97+ this .item = element ;
98+ this .next = next ;
99+ this .prev = prev ;
100+ }
101+ }
102+
103+ private Node GetNodeByIndex (int index ){
104+ if (index > size /2 )
105+ {
106+ Node Temp = first ;
107+ for (int i = 0 ; i < index ;i ++)
108+ Temp = Temp .next ; //
109+ return Temp ;
110+ }
111+ else
112+ {
113+ Node Temp = last ;
114+ for (int i = size -1 ; i > index ; i --)
115+ Temp = Temp .prev ;
116+ return Temp ;
117+ }
118+ }
119+
120+ private void checkPosition (int index ){
121+ if (index < 0 || index > size )
122+ throw new IndexOutOfBoundsException ("index:" + index +"is llegal" );
123+ }
124+ }
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